The usage of mobile broadband services using cellular networks has shown a significant increase during recent years. In parallel, there is an ongoing evolution of third and fourth generation cellular communication networks such as High Speed Packet Access, Long Term Evolution (LTE), and Worldwide Interoperability for Microwave Access in order to support an ever increasing performance with regards to capacity, peak bit rates and coverage. Operators deploying these networks are faced with a number of challenges, e.g. related to site and transport costs, and availability, as well as lack of wireless spectrum. Many different techniques are considered for meeting these challenges and for providing cost efficient mobile broadband.
One option available to the operators is to use shared network infrastructure and sites, i.e. when multiple cellular operators agree to deploy their network together. This is beneficial since it reduces the total deployment costs, and may further provide benefits due to pooling of the available spectrum. The drawback with network sharing in its current form is that it requires significant cooperation between the operators sharing the network since the network configuration is common for the part of the network that is shared, making it difficult to differentiate the treatment of users from each operator. This also makes interaction, e.g. handover, between shared parts and non-shared parts more complex, since the shared part needs to interact with a multiple of non-shared networks.
The support for network sharing has recently been enhanced in the third Generation Partnership Project (3GPP) Universal Terrestrial Radio Access Network (UTRAN) and Evolved-UTRAN standards. The standards allow various scenarios for network sharing, but it is expected that a common scenario will be when the Radio Access Network (RAN) is shared and each operator has its own Core Network (CN). This scenario is called Multi-Operator Core Network (MOCN) in 3GPP. From a technical point of view the MOCN configuration uses the multi-to-multi connectivity of the Iu and S1 interfaces between the Radio Network Controller (RNC) and CN, and the evolved Node B (eNB) and the CN, respectively. This makes it possible to connect a Radio Access Network (RAN) node, e.g. RNC or eNB, to multiple CN nodes, e.g. Serving General Packet Radio Service Support Node and Mobile Management Entity (MME), belonging to different operators. The RAN will in this configuration broadcast one Public Land Mobile Network (PLMN) identity for each operator sharing the RAN. The UE will at initial attach select which PLMN it wants to connect to and the RAN will make sure that the initial attach signaling is routed to the correct operators CN. Once the UE has been assigned a CN node there are also mechanisms making it possible for the RAN and CN to route subsequent signaling related to this UE to the same CN node. Besides the list of PLMN IDs, most system information broadcasted on the cell broadcast channels in the shared RAN is common for all operators sharing the RAN.
Another network sharing configuration which may be considered is the, so called, Multi-Operator Random Access Network (MORAN) configuration where operators share the physical network equipment but does not share the spectrum, i.e. each operator use different carriers. The advantage with the MORAN configuration is that each operator has full control over the configuration of broadcast parameters used in their spectrum, giving more freedom to have operator specific configurations. The drawback however is that the operators are not able to benefit from spectrum sharing leading to lower utilization of radio resource and lower network capacity, as compared to MOCN. The MORAN configuration has no standard impacts since the traffic from different operators are handled on separate carriers.
Another option for increasing the capacity and peak rates in 3GPP cellular networks is to use carrier aggregation. The principle for carrier aggregation is that a given UE may be served by multiple carriers at the same time, while it was previously only possible for a UE to use one carrier at a given time.
FIG. 1 illustrates a potential deployment scenario for carrier aggregation of the prior art. FIG. 1 further illustrates a base station 102 near which a UE 104 is located. Further, antennas of the base station are directed to define the coverage of a first carrier 106 of a first PLMN and the coverage of a second carrier 108 of a second PLMN. The UE is located in an area within the coverage of both the first carrier and the second carrier.
Carrier aggregation leads to that the maximum bit rate for a given UE may be increased and to an increase in the network capacity due to better resource utilization. The principle adopted for carrier aggregation in 3GPP is that the UE is assigned a Primary Component Carrier (PCC) on which it receives most of the control information. Transmission of data may however be performed on both the primary component carrier and on one or more Secondary Component Carriers (SCCs). Carrier aggregation in LTE may operate both in modes where the UE receives downlink/uplink scheduling commands on the primary component carrier only, as well in modes where the UE receives scheduling commands on all component carriers. Regardless of the mode of operation, the UE will only need to read the broadcast channel in order to acquire system information parameters on the PCC. System information related to the SCCs may be provided to the UE in dedicated Radio Resource Control (RRC) messages.
As mentioned above one drawback of supporting RAN sharing with spectrum sharing is that the operators need to have common parameter settings, e.g. system information setting, in the shared part of their network. Due to different loads, and service mix, for instance, it is desirable for operators to apply operator specific configurations.
It is of course possible to share the physical equipment only but then assign at least one carrier to each operator to use on its own, i.e. the MORAN configuration. This would enable each operator to apply operator specific configurations. The drawback would however be that there is no sharing of the spectrum between the operators.
There is thus a need to overcome the drawbacks of prior art configurations.